Method for transmitting and receiving synchronization signal in wireless communication system and apparatus for method

ABSTRACT

Disclosed are a method for transmitting and receiving a synchronization signal in a wireless communication system and an apparatus therefor. Specifically, a method for performing synchronization signal by transmitting and receiving a synchronization signal includes: receiving, from a base station, a primary synchronization signal (PSS) and a secondary synchronization signal (SSS); and performing synchronization by using the received PSS and the received SSS, in which a sequence for the SSS may be generated by a product between a first sequence and a second sequence and the number of first sequences may be configured to be larger than the number of second sequences.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/064,244, filed on Jun. 20, 2018, now allowed, which is the NationalStage filing under 35 U.S.C. 371 of International Application No.PCT/KR2017/010809, filed on Sep. 28, 2017, which claims the benefit ofU.S. Provisional Application No. 62/401,937, filed on Sep. 30, 2016,U.S. Provisional Application No. 62/417,357, filed on Nov. 4, 2016, U.S.Provisional Application No. 62/418,851, filed on Nov. 8, 2016, and U.S.Provisional Application No. 62/545,061, filed on Feb. 3, 2017. Thedisclosures of the prior applications are incorporated by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method for transmitting and receiving asynchronization signal by a user equipment and an apparatus forsupporting the same.

BACKGROUND

Mobile communication systems have been generally developed to providevoice services while guaranteeing user mobility. Such mobilecommunication systems have gradually expanded their coverage from voiceservices through data services up to high-speed data services. However,as current mobile communication systems suffer resource shortages andusers demand even higher-speed services, development of more advancedmobile communication systems is needed.

The requirements of the next-generation mobile communication system mayinclude supporting huge data traffic, a remarkable increase in thetransfer rate of each user, the accommodation of a significantlyincreased number of connection devices, very low end-to-end latency, andhigh energy efficiency. To this end, various techniques, such as smallcell enhancement, dual connectivity, massive multiple input multipleoutput (MIMO), in-band full duplex, non-orthogonal multiple access(NOMA), supporting super-wide band, and device networking, have beenresearched.

SUMMARY

This specification proposes a method for transmitting and receiving asynchronization signal in a wireless communication system.

This specification proposes a method for configuring and allocating asequence of a synchronization signal by considering a subcarrierspacing, a cyclic prefix (CP) length, or a bandwidth applied to thesynchronization signal.

More specifically, this specification proposes a method for generating asequence of a synchronization signal and mapping the generated sequenceto a resource region when a subcarrier spacing applied to asynchronization signal (e.g., PSS, SSS) and a default subcarrier spacingare configured to be equal to or different from each other.

Further, this specification proposes a method for generating a sequence(e.g., PSS sequence, SSS sequence) of a synchronization signal used fordistinguishing a cell identifier and mapping the generated sequence to aresource region.

The technical objects of the present invention are not limited to theaforementioned technical objects, and other technical objects, which arenot mentioned above, will be apparently appreciated by a person havingordinary skill in the art from the following description.

In an embodiment of the present invention, a method for performingsynchronization signal by a UE in a wireless communication systemincludes: receiving, from a base station, a primary synchronizationsignal (PSS) and a secondary synchronization signal (SSS); andperforming synchronization by using the received PSS and the receivedSSS, in which a sequence for the SSS is generated by a product between afirst sequence and a second sequence and the number of first sequencesis configured to be larger than the number of second sequences.

Furthermore, in the method according to the embodiment of the presentinvention, the number of sequences for the SSS may be configured to beequal to the number of cell identifiers.

Furthermore, in the method according to the embodiment of the presentinvention, the number of cell identifiers may be equal to the product ofthe number of first sequences and the number of second sequences.

Furthermore, in the method according to the embodiment of the presentinvention, the product between the first sequence and the secondsequence may be the product between each element of the first sequenceand each element of the second sequence.

Furthermore, in the method according to the embodiment of the presentinvention, each of a length of the first sequence and a length of thesecond sequence may be equal to the length of the sequence for the SSS.

Furthermore, in the method according to the embodiment of the presentinvention, any one of the first sequence and the second sequence may bean M sequence.

Furthermore, in the method according to the embodiment of the presentinvention, the M sequence may be generated based on a specific initialvalue and a specific cyclic shift.

Furthermore, in the method according to the embodiment of the presentinvention, a polynomial for the sequence for the PSS may be configuredto be equal to any one of a first polynomial for the first sequence anda second polynomial for the second sequence.

Furthermore, in the method according to the embodiment of the presentinvention, when the polynomial for the sequence for the PSS is x(n),x(0) may be 0, x(1) may be 1, x(2) may be 1, x(3) may be 0, x(4) may be1, x(5) may be 1, and x(6) may be 1, when the first polynomial is x₀(n),x₀(0) is 1, x₀(1) may be 0, x₀(2) may be 0, x₀(3) may be 0, x₀(4) may be0, x₀(5) may be 0, and x₀(6) may be 0, and when the second polynomial isx₁(n), x₁(0) may be 1, x₁(1) may be 0, x₁(2) may be 0, x₁(3) may be 0,x₁(4) may be 0, x₁(5) may be 0, and x₁(6) may be 0.

Furthermore, in the method according to the embodiment of the presentinvention, the SSS may be received contiguously with a physicalbroadcast channel (PBCH) and a cyclic prefix applied to the SS may beconfigured to be equal to the cyclic prefix applied to the PBCH.

In an embodiment of the present invention, a user equipment (UE)performing synchronization in a wireless communication system includes:a transceiving unit for transmitting and receiving a radio signal; and aprocessor functionally connected to the transceiving unit, in which theprocessor controls to receive, from a base station, a primarysynchronization signal (PSS) and a secondary synchronization signal(SSS) and perform synchronization by using the received PSS and thereceived SSS, a sequence for the SSS is generated by a product between afirst sequence and a second sequence, and the number of first sequencesis configured to be larger than the number of second sequences.

Furthermore, in the UE according to the embodiment of the presentinvention, the number of sequences for the SSS may be configured to beequal to the number of cell identifiers.

Furthermore, in the UE according to the embodiment of the presentinvention, the number of cell identifiers may be equal to the product ofthe number of first sequences and the number of second sequences.

Furthermore, in the UE according to the embodiment of the presentinvention, the product between the first sequence and the secondsequence may be the product between each element of the first sequenceand each element of the second sequence.

Furthermore, in the UE according to the embodiment of the presentinvention, each of a length of the first sequence and a length of thesecond sequence may be equal to the length of the sequence for the SSS.

Furthermore, in the UE according to the embodiment of the presentinvention, any one of the first sequence and the second sequence may bean M sequence.

According to an embodiment of the present invention, even when the samesubcarrier spacing or different subcarrier spacings are applied to aprimary synchronization signal and a secondary synchronization signal,high correlation performance can be maintained.

Further, according to an embodiment of the present invention, when asequence of a synchronization signal is generated, as not a shortsequence but a long sequence is used, a ghost effect can be preventedand cross-correlation performance can be enhanced.

In addition, according to an embodiment of the present invention, whenthe sequence of the synchronization signal is generated, the numbers ofcandidates for two different sequences used for the generation areconfigured to be different from each other (that is, the numbers ofcandidates of two sequences are configured to be uneven), and as aresult, the cross-correlation performance can be enhanced.

Advantages which can be obtained in the present invention are notlimited to the aforementioned effects and other unmentioned advantageswill be clearly understood by those skilled in the art from thefollowing description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included herein as a part of adescription in order to help understanding of the present disclosure,provide embodiments of the present disclosure, and describe thetechnical features of the present disclosure with the description below.

FIG. 1 illustrates an example of an overall structure of a new radio(NR) system to which a method proposed by the present disclosure may beimplemented.

FIG. 2 illustrates a relationship between a uplink (UL) frame and adownlink (DL) frame in a wireless communication system to which a methodproposed by the present disclosure may be implemented.

FIG. 3 illustrates an example of a resource grid supported in a wirelesscommunication system to which a method proposed by the presentdisclosure may be implemented.

FIG. 4 illustrates examples of resource grids for each antenna port andnumerology to which a method proposed in this specification may beapplied.

FIG. 5 illustrates an example of a self-contained subframe structure towhich the method proposed in this specification may be applied.

FIG. 6 illustrates an example of a method for transmitting asynchronization signal to which a method proposed in this specificationmay be applied.

FIGS. 7A and 7B illustrate another example of the method fortransmitting the synchronized signal to which the method proposed inthis specification may be applied.

FIG. 8 illustrates yet another example of the method for transmittingthe synchronization signal to which the method proposed in thisspecification may be applied.

FIG. 9 illustrates still yet another example of the method fortransmitting the synchronization signal to which the method proposed inthis specification may be applied.

FIG. 10 illustrates still yet another example of the method fortransmitting the synchronization signal to which the method proposed inthis specification may be applied.

FIG. 11 illustrates an operation flowchart of a user equipment whichperforms synchronization through transmission and reception of asynchronization signal to which a method proposed in this specificationmay be applied.

FIG. 12 illustrates a block diagram of a wireless communication deviceto which methods proposed in this specification may be applied.

FIG. 13 illustrates a block diagram of a communication device accordingto an embodiment of the present invention.

DETAILED DESCRIPTION

Some embodiments of the present disclosure are described in detail withreference to the accompanying drawings. A detailed description to bedisclosed along with the accompanying drawings is intended to describesome exemplary embodiments of the present disclosure and is not intendedto describe a sole embodiment of the present disclosure. The followingdetailed description includes more details in order to provide fullunderstanding of the present disclosure. However, those skilled in theart will understand that the present disclosure may be implementedwithout such more details.

In some cases, in order to avoid making the concept of the presentdisclosure vague, known structures and devices are omitted or may beshown in a block diagram form based on the core functions of eachstructure and device.

In the present disclosure, a base station has the meaning of a terminalnode of a network over which the base station directly communicates witha terminal. In this document, a specific operation that is described tobe performed by a base station may be performed by an upper node of thebase station according to circumstances. That is, it is evident that ina network including a plurality of network nodes including a basestation, various operations performed for communication with a terminalmay be performed by the base station or other network nodes other thanthe base station. The base station (BS) may be substituted with anotherterm, such as a fixed station, a Node B, an eNB (evolved-NodeB), a basetransceiver system (BTS), or an access point (AP). Furthermore, theterminal may be fixed or may have mobility and may be substituted withanother term, such as user equipment (UE), a mobile station (MS), a userterminal (UT), a mobile subscriber station (MSS), a subscriber station(SS), an advanced mobile station (AMS), a wireless terminal (WT), amachine-type communication (MTC) device, a machine-to-Machine (M2M)device, or a device-to-device (D2D) device.

Hereinafter, downlink (DL) means communication from a base station toUE, and uplink (UL) means communication from UE to a base station. InDL, a transmitter may be part of a base station, and a receiver may bepart of UE. In UL, a transmitter may be part of UE, and a receiver maybe part of a base station.

Specific terms used in the following description have been provided tohelp understanding of the present disclosure, and the use of suchspecific terms may be changed in various forms without departing fromthe technical sprit of the present disclosure.

The following technologies may be used in a variety of wirelesscommunication systems, such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and non-orthogonalmultiple access (NOMA). CDMA may be implemented using a radiotechnology, such as universal terrestrial radio access (UTRA) orCDMA2000. TDMA may be implemented using a radio technology, such asglobal system for mobile communications (GSM)/general packet radioservice (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA maybe implemented using a radio technology, such as Institute of electricaland electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),IEEE 802.20, or evolved UTRA (E-UTRA). UTRA is part of a universalmobile telecommunications system (UMTS). 3rd generation partnershipproject (3GPP) Long term evolution (LTE) is part of an evolved UMTS(E-UMTS) using evolved UMTS terrestrial radio access (E-UTRA), and itadopts OFDMA in downlink and adopts SC-FDMA in uplink. LTE-advanced(LTE-A) is the evolution of 3GPP LTE.

Embodiments of the present disclosure may be supported by the standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2, thatis, radio access systems. That is, steps or portions that belong to theembodiments of the present disclosure and that are not described inorder to clearly expose the technical spirit of the present disclosuremay be supported by the documents. Furthermore, all terms disclosed inthis document may be described by the standard documents.

In order to more clarify a description, 3GPP LTE/LTE-A is chieflydescribed, but the technical characteristics of the present disclosureare not limited thereto.

As propagation of smart phones and Internet of things (IoT) terminalsrapidly spreads, the amount of information which is transmitted andreceived through a communication network increases. Accordingly, thenext generation wireless access technology is an environment (e.g.,enhanced mobile broadband communication) that provides a faster serviceto more users than existing communication systems (or existing radioaccess technology) needs to be considered.

To this end, a design of a communication system that considers machinetype communication (MTC) providing a service by connecting multipledevices and objects is discussed. Further, a design of a communicationsystem (e.g., Ultra-Reliable and Low Latency Communication (URLLC))considering a service and/or a user equipment sensitive to reliabilityand/or latency of communication is also discussed.

Hereinafter, in this specification, for easy description, thenext-generation wireless access technology is referred to as a new radioaccess technology (RAT) (NR) radio access technology and the wirelesscommunication system to which the NR is applied is referred to as an NRsystem.

Definition of Terms

eLTE eNB: An eLTE eNB is an evolution of an eNB that supports aconnection for an EPC and an NGC.

gNB: A node for supporting NR in addition to a connection with an NGC

New RAN: A radio access network that supports NR or E-UTRA or interactswith an NGC

Network slice: A network slice is a network defined by an operator so asto provide a solution optimized for a specific market scenario thatrequires a specific requirement together with an inter-terminal range.

Network function: A network function is a logical node in a networkinfra that has a well-defined external interface and a well-definedfunctional operation.

NG-C: A control plane interface used for NG2 reference point between newRAN and an NGC

NG-U: A user plane interface used for NG3 reference point between newRAN and an NGC

Non-standalone NR: A deployment configuration in which a gNB requires anLTE eNB as an anchor for a control plane connection to an EPC orrequires an eLTE eNB as an anchor for a control plane connection to anNGC

Non-standalone E-UTRA: A deployment configuration an eLTE eNB requires agNB as an anchor for a control plane connection to an NGC.

User plane gateway: A terminal point of NG-U interface

General System

FIG. 1 is a diagram illustrating an example of an overall structure of anew radio (NR) system to which a method proposed by the presentdisclosure may be implemented.

Referring to FIG. 1, an NG-RAN is composed of gNBs that provide an NG-RAuser plane (new AS sublayer/PDCP/RLC/MAC/PHY) and a control plane (RRC)protocol terminal for a UE (User Equipment).

The gNBs are connected to each other via an Xn interface.

The gNBs are also connected to an NGC via an NG interface.

More specifically, the gNBs are connected to a Access and MobilityManagement Function (AMF) via an N2 interface and a User Plane Function(UPF) via an N3 interface.

NR (New Rat) Numerology and Frame Structure

In the NR system, multiple numerologies may be supported. Thenumerologies may be defined by subcarrier spacing and a CP (CyclicPrefix) overhead. Spacing between the plurality of subcarriers may bederived by scaling basic subcarrier spacing into an integer N (or μ). Inaddition, although a very low subcarrier spacing is assumed not to beused at a very high subcarrier frequency, a numerology to be used may beselected independent of a frequency band.

In addition, in the NR system, a variety of frame structures accordingto the multiple numerologies may be supported.

Hereinafter, an Orthogonal Frequency Division Multiplexing (OFDM)numerology and a frame structure, which may be considered in the NRsystem, will be described.

A plurality of OFDM numerologies supported in the NR system may bedefined as in Table 1.

TABLE 1 μ Δf = 2^(μ) · 15 [kHz] Cyclic prefix 0  15 Normal 1  30 Normal2  60 Normal, Extended 3 120 Normal 4 240 Normal 5 480 Normal

Regarding a frame structure in the NR system, a size of various fieldsin the time domain is expressed as a multiple of a time unit ofT_(s)=1/(Δf_(max)·N_(f)). In this case, Δf_(max)=480·10³, andN_(f)=4096. DL and UL transmission is configured as a radio frame havinga section of T_(f)=(Δf_(max)N_(f)/100)·T_(s)10 ms. The radio frame iscomposed of ten subframes each having a section ofT_(sf)=(Δf_(max)N_(f)/1000)·T_(s)=1 ms. In this case, there may be a setof UL frames and a set of DL frames.

FIG. 2 illustrates a relationship between a UL frame and a DL frame in awireless communication system to which a method proposed by the presentdisclosure may be implemented.

As illustrated in FIG. 2, a UL frame number I from a User Equipment (UE)needs to be transmitted T_(TA)=N_(TA)T_(s) before the start of acorresponding DL frame in the UE.

Regarding the numerology μ, slots are numbered in ascending order ofn_(s) ^(μ)ϵ{0, . . . , N_(subframe) ^(slots,μ)−1} in a subframe, and inascending order of n_(s,f) ^(μ)ϵ{0, . . . , N_(frame) ^(slots,μ)−1} in aradio frame. One slot is composed of continuous OFDM symbols of N_(symb)^(μ), and N_(symb) ^(μ) is determined depending on a numerology in useand slot configuration. The start of slots n_(s) ^(μ) in a subframe istemporally aligned with the start of OFDM symbols n_(s) ^(μ)N_(symb)^(μ) the same subframe.

Not all UEs are able to transmit and receive at the same time, and thismeans that not all OFDM symbols in a DL slot or an UL slot are availableto be used.

Table 2 shows the number of OFDM symbols per slot for a normal CP in thenumerology μ, and Table 3 shows the number of OFDM symbols per slot foran extended CP in the numerology μ.

TABLE 2 Slot configuration 0 1 μ N_(symb) ^(μ) N_(frame) ^(slots,μ)N_(subframe) ^(slots,μ) N_(symb) ^(μ) N_(frame) ^(slots,μ) N_(subframe)^(slots,μ) 0 14 10 1 7 20 2 1 14 20 2 7 40 4 2 14 40 4 7 80 8 3 14 80 8— — — 4 14 160 16 — — — 5 14 320 32 — — —

TABLE 3 Slot configuration 0 1 μ N_(symb) ^(μ) N_(frame) ^(slots,μ)N_(subframe) ^(slots,μ) N_(symb) ^(μ) N_(frame) ^(slots,μ) N_(subframe)^(slots,μ) 0 12 10 1 6 20 2 1 12 20 2 6 40 4 2 12 40 4 6 80 8 3 12 80 8— — — 4 12 160 16 — — — 5 12 320 32 — — —

NR Physical Resource

Regarding physical resources in the NR system, an antenna port, aresource grid, a resource element, a resource block, a carrier part,etc. may be considered.

Hereinafter, the above physical resources possible to be considered inthe NR system will be described in more detail.

First, regarding an antenna port, the antenna port is defined such thata channel over which a symbol on one antenna port is transmitted can beinferred from another channel over which a symbol on the same antennaport is transmitted. When large-scale properties of a channel receivedover which a symbol on one antenna port can be inferred from anotherchannel over which a symbol on another antenna port is transmitted, thetwo antenna ports may be in a QC/QCL (quasi co-located or quasico-location) relationship. Herein, the large-scale properties mayinclude at least one of delay spread, Doppler spread, Doppler shift,average gain, and average delay.

FIG. 3 illustrates an example of a resource grid supported in a wirelesscommunication system to which a method proposed by the presentdisclosure may be implemented.

Referring to FIG. 3, a resource grid is composed of N_(RB) ^(μ)N_(sc)^(RB) carriers in a frequency domain, each subframe composed of 14·2μOFDM symbols, but the present disclosure is not limited thereto.

In the NR system, a transmitted signal is described by one or moreresource grids, composed of N_(RB) ^(μ)N_(sc) ^(RB) subcarriers, and2^(μ)N_(symb) ^((μ)) OFDM symbols Herein, N_(RB) ^(μ)≤N_(RB) ^(max,μ).The above RB indicates the maximum transmission bandwidth, and it maychange not just between numerologies, but between UL and DL.

In this case, as illustrated in FIG. 4, one resource grid may beconfigured for the numerology μ and an antenna port p.

FIG. 4 shows an example of antenna ports and ringer-specific resourcegrids to which the method proposed herein can be applied.

Each element of the resource grid for the numerology μ and the antennaport p is indicated as a resource element, and may be uniquelyidentified by an index pair (k,l). Herein, k=0, . . . , N_(RB)^(μ)N_(sc) ^(RB)−1 is an index in the frequency domain, and l=0, . . . ,2^(μ)N_(symb) ^((μ))−1 indicates a location of a symbol in a subframe.To indicate a resource element in a slot, the index pair (k,l) is used.Herein, l=0, . . . , N_(symb) ^(μ)−1.

The resource element (k,l) for the numerology μ and the antenna port pcorresponds to a complex value a_(k,l) ^((p,μ)). When there is no riskof confusion or when a specific antenna port or numerology is specified,the indexes p and μ may be dropped and thereby the complex value maybecome a_(k,l) ^((p)) or a_(k,l) .

In addition, a physical resource block is defined as N_(sc) ^(RB)=12continuous subcarriers in the frequency domain. In the frequency domain,physical resource blocks may be numbered from 0 to N_(RB) ^(μ)−1. Atthis point, a relationship between the physical resource block numbern_(PRB) and the resource elements (k,l) may be given as in Equation 1.

$\begin{matrix}{n_{PRB} = \left\lfloor \frac{k}{N_{sc}^{RB}} \right\rfloor} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In addition, regarding a carrier part, a UE may be configured to receiveor transmit the carrier part using only a subset of a resource grid. Atthis point, a set of resource blocks which the UE is configured toreceive or transmit are numbered from 0 to N_(URB) ^(μ)−1 in thefrequency region.

Synchronization Signal (SS) and SS/PBCH Block

(1) Synchronization Signal

With respect to a physical layer cell identity, 1008 physical layer cellidentities may be given by Equation 2.

N _(ID) ^(cell)=3N _(ID) ⁽¹⁾ +N _(ID) ⁽²⁾  Equation 2

In Equation 2, N_(ID) ⁽¹⁾ϵ{0, 1, . . . , 335} and N_(ID) ⁽²⁾ϵ{0, 1, 2}.

Further, with respect to the primary synchronization signal (PSS), asequence d_(PSS)(n) for the PSS may be defined by Equation 3.

d _(PSS)(n)=1−2x(m) m=(n+43N _(ID) ⁽²⁾)mod127 0≤n<127  Equation 3

In Equation 3, x(m) (i.e., a polynomial for generating the sequence ofthe PSS) may be configured as shown in Equation 4 and an initial value(i.e., initial poly shift register value or an initial condition) isshown in Equation 5.

x(i+7)=(x(i+4)+x(i))mod2  Equation 4

[x(6)x(5)x(4)x(3)x(2)x(1)x(0)]=[1 1 0 1 1 0]

Further, with respect to a secondary synchronization signal (SSS), asequence d_(sSS)(n) for the SSS may be defined by Equation 6.

$\begin{matrix}{{d_{SSS}(n)} = {\left\lbrack {1 - {2{x_{0}\left( {\left( {n + m_{0}} \right){mod}\ 127} \right)}}} \right\rbrack {\quad{{\left\lbrack {1 - {2{x_{1}\left( {\left( {n + m_{1}} \right){mod}\ 127} \right)}}} \right\rbrack \mspace{20mu} m_{0}} = {{{15\left\lfloor \frac{N_{ID}^{(1)}}{112} \right\rfloor} + {5N_{ID}^{(2)}\mspace{20mu} m_{1}}} = {{N_{ID}^{(1)}\mspace{14mu} {mod}\; 112\mspace{20mu} 0} \leq n < {127}}}}}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

In Equation 6, x₀(m) and x₁(m) (i.e., a first polynomial and a secondpolynomial for generating the sequence of the SSS) may be configured asshown in Equation 7 and each initial value (i.e., initial poly shiftregister value) is shown in Equation 8.

x ₀(i+7)=(x ₀(i+4)+x ₀(i))mod2

x ₁(i+7)=(x ₁(i+1)+x ₁(i))mod2  Equation 7

[x ₀(6) x ₀(5) x ₀(4) x ₀(3) x ₀(2) x ₀(1) x ₀(0)]=[0 0 0 0 0 0 1]

[x ₁(6) x ₁(5) x ₁(4) x ₁(3) x ₁(2) x ₁(1) x ₁(0)]=[0 0 0 0 0 0 1]

In this case, referring to Equations 4 and 7, one (i.e., x₀(m)) of thepolynomials for generating the sequence of the SSS is configured to beequal to the polynomial (i.e., x(m)) for generating the sequence of thePSS. However, the initial value of the polynomial for generating thesequence of the PSS is configured to be different from the initial valueof the polynomial for generating the sequence of the SSS.

(2) SS/PBCH Block

Contents related to a time-frequency structure of the SS/PBCH block willbe described. In the time domain, the SS/PBCH block constitutes fourOFDM symbols numbered from 0 to 3 in order. Further, in the frequencydomain, the SS/PBCH block constitutes 24 contiguous resource blocksnumbered from 0 to 287 in order and starts with the lowest numberedresource block.

The UE needs to assume a sequence d_(PSS)(0), . . . , d_(PSS)(126) ofsymbols constituting the PSS, which are to be scaled by an elementβ_(SS) and mapped to resource elements (k,l)_(p,μ) in an ascending orderof k to follow PSS power allocation. Here, k and l are given by Table 4below and represent a frequency index and a time index in the SS/PBCHblock, respectively.

Further, the UE needs to assume a sequence d_(SSS)(0), . . . ,d_(SSS)(126) of symbols constituting the PSS, which are to be scaled byan element β_(SS) and mapped to resource elements (k,l)_(p,μ) in anascending order of k to follow SSS power allocation. Here, k and l aregiven by Table 4 below and represent the frequency index and the timeindex in the SS/PBCH block, respectively.

Further, the UE needs to assume a sequence d_(PBCH)(0), . . . ,d_(PBCH)(M_(symb)−1) of complex-valued symbols constituting the PBCH,which are to be scaled by an element β_(PBCH) and mapped to resourceelements (k,l)_(p,μ) in order starting with d_(PBCH)(0) to follow PBCHpower allocation. Here, the resource elements are not for PBCHdemodulation reference signals.

Mapping for resource elements that are not reserved for other purposesfirst increases in the order of index k and then increases for index 1.Here, k and l are given by Table 4 below and represent the frequencyindex and the time index in the SS/PBCH block, respectively.

Further, the UE needs to assume a sequence r₁(0), . . . , r₁(71) ofcomplex-valued symbols constituting the demodulated reference signal forthe PBCH in symbol I of the SS/PBCH block, which are to be scaled by anelement β_(PBCH) and mapped to resource elements (k,l)_(p,μ) in orderstarting with k to follow the PBCH power allocation. Here, k and l aregiven by Table 4 below and represent the frequency index and the timeindex in the SS/PBCH block, respectively.

Further, the UE needs to assume that the antenna port is 4000 (i.e.,p=4000) and a subcarrier spacing configuration is μϵ{0, 1, 3, 4} for theSS/PBCH block and needs to assume the same cyclic prefix (CP) length andsubcarrier spacing for the PSS, SSS, and PBCH.

TABLE 4 Channel or signal OFDM symbol number ^(l) Subcarrier number ^(k)PSS 0 80, 81, . . . , 206 SSS 2 80, 81, . . . , 206 PBCH 1, 3 0, 1, . .. , 287 DM-RS for 1, 3 2, 6, 10, 14, 18, . . . , PBCH 282, 286

Further, with respect to a time location of the SS/PBCH block, the UEneeds to monitor available SS/PBCH blocks at predefined time domainlocations on the standard (specification).

Self-Contained Subframe Structure

A time division duplexing (TDD) structure considered in the NR system isa structure in which both uplink (UL) and downlink (DL) are processed inone subframe. This is to minimize the latency of data transmission inthe TDD system and the structure is referred to as a self-containedsubframe structure.

FIG. 5 illustrates an example of a self-contained subframe structure towhich the method proposed in this specification may be applied. FIG. 5is just for convenience of the description and does not limit the scopeof the present invention.

Referring to FIG. 5, it is assumed that one subframe is constituted by14 orthogonal frequency division multiplexing (OFDM) symbols as inlegacy LTE.

In FIG. 5, a region 502 refers to a downlink control region and a region504 refers to an uplink control region. Further, a region (that is, aregion without a separate indication) other than the regions 502 and 504may be used for transmitting downlink data or uplink data.

That is, uplink control information and downlink control information maybe transmitted in one self-contained subframe. On the contrary, uplinkdata or downlink data is transmitted in one self-contained subframe.

When the structure illustrated in FIG. 2 is used, in one self-containedsubframe, downlink transmission and uplink transmission may sequentiallyproceed and transmission of the downlink data and reception of uplinkACK/NACK may be performed.

Consequently, when an error of data transmission occurs, a time requiredfor retransmitting data may be reduced. Therefore, latency associatedwith data delivery may be minimized.

In the self-contained subframe structure illustrated in FIG. 5, a timegap for a process of switching from a transmission mode to a receptionmode in a base station (eNodeB, eNB, or gNB) and/or a terminal (userequipment (UE)) or a process of switching from the reception mode to thetransmission mode is required. In association with the time gap, whenthe uplink transmission is performed after the downlink transmission inthe self-contained subframe, some OFDM symbol(s) may be configured as aguard period (GP).

Analog Beamforming

In a millimeter wave (mmWave, mmW) communication system, as thewavelength of the signal becomes shorter, multiple (or multiplex)antennas may be installed in the same area. For example, in a 30 CHzband, the wavelength is approximately 1 cm, and when antennas areinstalled at an interval of 0.5 lambda in a panel of 5 cm×5 cm accordingto a two-dimensional arrangement form, a total of 100 antenna elementsmay be installed.

Accordingly, in the mmW communication system, a method for increasingcoverage or increasing the throughput by increasing a beamforming (BF)gain using multiple antenna elements or increasing a throughput may beconsidered.

In this case, when a transceiver unit (TXRU) is installed so as toadjust transmission power or a phase for each antenna element,independent beamforming is possible for each frequency resource.

However, a method for installing the TXRU in all antenna elements (e.g.,100 antenna elements) may be ineffective in terms of cost. As a result,a method for mapping multiple antenna elements to one TXRU andcontrolling a direction of a beam by using an analog phase shifter maybe considered.

The aforementioned analog beamforming method may generate only one beamdirection in all bands, so that a frequency selective beam operation maynot be performed.

As a result, hybrid beamforming with B TXRUs that are fewer than Qantenna elements, as an intermediate form of digital beamforming andanalog beamforming, may be considered. In this case, although there is adifference depending on a connection method of B TXRUs and Q antennaelements, the number of directions of the beams that may be transmittedat the same time is limited to B or less.

Hereinafter, in this specification, contents regarding a synchronizationsignal that may be used when a frame structure in which two or moredifferent numerologies are simultaneously present at the same frequencyand/or the same time point is considered will be described.

In order to distinguish the corresponding system from the legacy LTEsystem, a physical signal and/or a physical channel used in thecorresponding system may be designated (or defined) as an x-PrimarySynchronization signal (PSS), an x-Secondary Synchronization Signal(SSS), an x-Physical Broadcast Channel (PBCH), an x-Physical DownlinkControl Channel (PDCCH)/x-Enhanced PDCCH (EPDCCH), etc to which ‘x-’ isadded. Here, the ‘x’ may refer to ‘NR’. The synchronization signal (SS)considered in this specification refers to signals used by the UE toperform synchronization, such as x-PSS, x-SSS, and/or x-PBCH.

Two synchronization signal design methods may be considered when two ormore different numerologies (e.g., subcarrier spacing, etc.) co-exist.

First, a method for transmitting a different synchronization signal foreach numerology may be considered. However, in the case of the method,the system may have large synchronization overhead the UE may have highdecoding complexity. Next, a method may be considered, in which onedefault numerology is configured through a predetermined method (thatis, a preconfigured reference) between the base station and the UE amongmultiple numerologies and the synchronization signal is transmittedaccording to the configured default numerology. The method isadvantageous in that the decoding complexity and the synchronizationoverhead for the synchronization signal are small as compared with thefirst method described above.

In this specification, a method for transmitting and receiving thesynchronization signal according to one (i.e., single) defaultnumerology that is preconfigured between the base station and the UEamong multiple numerologies is described. In this case, the defaultnumerology for transmission of the synchronization signal may bedetermined independently in accordance with a frequency band (e.g., aband of 6 GHz or less, mmWave of 6 GHz or more, and the like).

In addition, the UE may be configured to obtain (or find out)information regarding the default numerology through blind decoding. Inthis case, in order to reduce the number of blind decodings for thedefault numerology, a candidate(s) may be preconfigured in which eachdefault numerology may be configured to a different value. For example,a scheme for mapping one numerology to one set by configuring twochannel raster sets (or channel raster configurations) may be used whenthere are two candidates for the default numerology. As an example, afirst numerology may be configured at 100 kHz and a second numerologymay be configured at 300 kHz.

Hereinafter, a method for designing (or configuring, generating) thesequence for the synchronization signal in a system in which the defaultnumerology is used will be described. Specifically, a method will bedescribed below, in which when a default frequency band to which thesynchronization signal is transmitted is preconfigured and when thefrequency band is configured to use the default numerology, a sequence(i.e., a sequence configured to the PSS, a sequence used to generate thePSS) which may be used as the primary synchronization signal (PSS) isconfigured and allocated. Further, in this specification, a method forconfiguring and assigning a sequence that may be used as not only thePSS but also a secondary synchronization signal (SSS) will also bedescribed.

In addition, it goes without saying that a sequence design scheme of thesynchronization signal described below in this specification may beapplied in the same or similar manner even when the default numerologyis not used.

First, some of the elements that may be considered to determine thedefault numerology and/or the numerology used (or applied) to thesynchronization signal are as follows.

-   -   Subcarrier spacing    -   Cyclic Prefix (CP) length    -   Bandwidth for synchronization signal

Hereinafter, the elements will be described in detail.

First, contents related to the subcarrier spacing are described. Ingeneral, a synchronization signal based on Cyclic Prefix-OrthogonalFrequency Division Multiplexing (CP-OFDM) may be sensitive to afrequency offset value. Therefore, in order to determine the subcarrierspacing, it is necessary to consider the frequency offset valueaccording to a carrier frequency value. According to a simulationassumption for the performance verification of the NR system, requiredfrequency offset values are different according to initial acquisitionand non-initial acquisition. Here, the initial acquisition and thenon-initial acquisition may mean initial acquisition and non-initialacquisition for the synchronization signal.

In the case of the initial acquisition, a transmission and receptionpoint (TRP) is considered to be a uniform distribution criterion +/−0.05ppm and in the case of the UE, the TRP may be considered to be theuniform distribution criterion +/−5, 10, 20 ppm. In contrast, in thecase of the non-initial acquisition, the TRP is considered to be theuniform distribution criterion +/−0.05 ppm and in the case of the UE,the TRP may be considered to be the uniform distribution criterion+/−0.1 ppm. In this case, the frequency offset values are calculatedaccording to the carrier frequency values using 5 ppm, 10 ppm, and 20ppm that are considered in the initial acquisition, as shown in Table 5below.

TABLE 5 Carrier Frequency (GHz) ppm 4 30 70 5 20 kHz 150 kHz 350 kHz 1040 kHz 300 kHz 700 kHz 20 80 kHz 600 kHz 1400 kHz 

The values in Table 5 are values calculated according to exemplarycarrier frequencies that may be considered in the NR system. Referringto Table 5, the carrier frequency offset tends to increase as thecarrier frequency increases. In general, an influence of the carrierfrequency offset may be important in an initial acquisition situation.Therefore, it is necessary to reduce the influence of the carrierfrequency offset on the synchronization signal (i.e., PSS).

In addition, Table 6 below shows normalized frequency offset valuesaccording to specific subcarrier spacing values for different carrierfrequency values.

TABLE 6 Subcarrier Spacing Carrier Frequency (GHz) (kHz) ppm 4 30 70 15 5 1.33 10 23.33 10 2.67 20 46.67 20 5.33 40 93.33 30  5 0.67 5 11.67 101.33 10 23.33 20 2.67 20 46.67 60  5 0.33 2.5 5.83 10 0.67 5 11.67 201.33 10 23.33 120  5 0.17 1.25 2.92 10 0.33 2.5 5.83 20 0.67 5 11.67 240 5 0.08 0.63 1.46 10 0.17 1.25 2.92 20 0.33 2.5 5.83 480  5 0.04 0.310.73 10 0.08 0.63 1.46 20 0.17 1.25 2.92

Referring to Table 6, the frequency offset value tends to decrease asthe subcarrier spacing value increases. That is, initial accessperformance may be enhanced as the subcarrier spacing value increases.Therefore, when considering 6 GHz or less (below 6 GHz) (i.e., when theanalog beamforming is not performed), a default subcarrier spacing isset to Δf_(d) and the subcarrier spacing of the synchronization signalmay be set to be N times (i.e., N*Δf_(d)) of the default subcarrierspacing. In this case, N may be set to a multiple of 2 or 2^(n) (here, nis a positive integer).

Further, the subcarrier spacing of signals such as the SSS and/or thePhysical Broadcast Channel (PBCH) rather than initial acquisition may beconfigured to use the same value as the subcarrier spacing (i.e., thesubcarrier spacing applied to the PSS) used by the PSS. However, sincethe SSS and the PBCH are not initially acquired, the SSS and the PBCHmay not be significantly affected by the frequency offset value. Thus,for the SSS and/or PBCH, a default subcarrier spacing (e.g., Δf_(d))rather than the subcarrier spacing (e.g., N*Δf_(d)) used by the PSS maybe configured.

Next, contents related to the CP length are described. In general, theCP length may be used to prevent Inter-Symbol Interference (ISI) causedby a delay spread. Further, since a symbol duration becomes shorter asthe subcarrier spacing becomes larger, the CP length may also becomeshorter as the subcarrier spacing becomes larger. Therefore, when asubcarrier spacing with a large value is used, the CP length isshortened, so that performance in a channel with a large delay spreadmay be degraded.

However, in order to support the NR system in a band (i.e., below 6 GHzband) of 6 GHz or less, the system needs to be configured toapproximately operate even in a channel (e.g., Extended Typical UrbanModel (ETU), Tapped-delay line, etc.) with a long delay spread.Therefore, considering the delay spread, it may be advantageous that theCP length may be configured to be larger.

Next, contents related to the bandwidth for the synchronization signalare described. A bandwidth used for the synchronization signal of theexisting LTE system (i.e., legacy LTE system) is 1.08 MHz. When, in theNR system, a subcarrier spacing with a value larger than the subcarrierspacing value of the existing LTE system is configured, a widerbandwidth is used for the synchronization signal. However, as thebandwidth to be received becomes wider, calculation complexity of the UEmay increase. Therefore, in order to prevent the calculation complexityfrom increasing, it may be desirable that the bandwidth to be used forthe synchronization signal of the NR system is kept similar to that ofthe LTE system.

Considering the above elements, there may be various methods fordesigning the synchronization signal of the NR system. In variousembodiments of the present invention, four following methods (Method 1to Method 4) may be considered. Hereinafter, in the methods, Δf_(d)represents the default subcarrier spacing and Δf_(PSS) and Δf_(SSS)represent subcarrier spacings used for PSS (i.e. NR PSS) and SSS (i.e.NR SSS), respectively.

(Method 1)

Method 1 is a method for configuring the subcarrier spacings to be used(or applied) to the PSS and the SSS to the same value as the defaultsubcarrier spacing (i.e., Δf_(d)=Δf_(PSS)=Δf_(SSS)). In other words,when the default subcarrier spacing to be used for each frequency bandis determined (or configured), the subcarrier spacings to be used forthe PSS and the SSS may be configured to be equal to the defaultsubcarrier spacing.

For example, when a default subcarrier spacing of 15 kHz is configuredfor a center frequency in the vicinity of 4 GHz or 6 GHz, the subcarrierspacings applied to the PSS and SSS may be configured to 15 kHz.However, when the subcarrier spacing for the synchronization signal isconfigured to 15 kHz (i.e., the subcarrier spacing of the LTE system) inthe band (below 6 GHz) of 6 GHz or less as described above (e.g., Table5), a frequency estimation (offset) operation of the PSS may be affectedby the carrier frequency offset.

As another example, when a default subcarrier spacing of 60 kHz isconfigured for the center frequency in the vicinity of 4 GHz or 6 GHz,the subcarrier spacings applied to the PSS and SSS may also beconfigured to 60 kHz. When the subcarrier spacing for thesynchronization signal is configured to 60 kHz higher than 15 kHz asdescribed above (e.g., Table 5), the frequency estimation (offset)operation of the PSS may be affected by the carrier frequency offset.

(Method 2)

Method 2 is a method (i.e., N*Δf_(d)=Δf_(PSS)=Δf_(SSS)) for configuringthe subcarrier spacings to be used for the PSS and the SSS to be equalto each other and configuring the subcarrier spacings that areconfigured to be equal to each other by scaling N times the defaultsubcarrier spacing. In other words, when the default subcarrier spacingto be used for each frequency band is determined (or configured), thesubcarrier spacings to be used for the PSS and the SSS may be configuredby scaling N times the default subcarrier spacing. In this case, N maybe scaled in the form of a multiple of two (i.e., N=(2n)±1, where n is apositive integer), or may be scaled in the form of to 2^(m) (i.e.,N=2^(m), where m is an integer).

For example, when the default subcarrier spacing of 15 kHz is configuredfor the center frequency in the vicinity of 4 GHz or 6 GHz, thesubcarrier spacings applied to the PSS and SSS may be configured to 60kHz acquired by scaling 4 times 15 kHz. Using the method, the frequencyestimation (offset) operation of the PSS may be less affected by thecarrier frequency offset.

(Method 3)

Method 3 is a method (i.e., N*Δf_(d)=Δf_(PSS), Δf_(d)=Δf_(SSS)) forconfiguring the subcarrier spacing to be used for the SSS to be equal tothe default subcarrier spacing and configuring the subcarrier spacing tobe used for the PSS by scaling N times the default subcarrier spacing.In other words, when the default subcarrier spacing to be used for eachfrequency band is determined (or configured), the subcarrier spacing tobe used for the PSS may be configured by scaling N times the defaultsubcarrier spacing and the subcarrier spacing to be used for the SSS maybe configured to be equal to the default subcarrier spacing.

For example, when the default subcarrier spacing of 15 kHz is configuredfor the center frequency in the vicinity of 4 GHz or 6 GHz, thesubcarrier spacing applied to the PSS may be configured to 60 kHz (N=4)and the subcarrier spacing applied to the SSS may be configured to 15kHz. In this case, since the frequency estimation (offset) operation ofthe PSS may be less affected by the carrier frequency offset and the CPlength in the SSS is the same as that of the existing LTE system, it isadvantageous in that a cell ID detecting operation may be efficientlyperformed even in the channel having the long delay spread.

(Method 4)

Method 4 is a method (i.e., Δf_(d)=Δf_(PSS), N*Δf_(d)=Δf_(SSS)) forconfiguring the subcarrier spacing to be used for the PSS to be equal tothe default subcarrier spacing and configuring the subcarrier spacing tobe used for the SSS by scaling N times the default subcarrier spacing.In other words, when the default subcarrier spacing to be used for eachfrequency band is determined (or configured), the subcarrier spacing tobe used for the SSS may be configured by scaling N times the defaultsubcarrier spacing and the subcarrier spacing to be used for the PSS maybe configured to be equal to the default subcarrier spacing.

For example, when the default subcarrier spacing of 15 kHz is configuredfor the center frequency in the vicinity of 4 GHz or 6 GHz, thesubcarrier spacing applied to the SSS may be configured to 60 kHz (N=4)and the subcarrier spacing applied to the PSS may be configured to 15kHz.

Further, in various embodiments of the present invention, differentsubcarrier spacings may be configured for the PSS and the SSS, as inMethod 3 and Method 4 described above. In this case, a method fortransmitting the PSS and/or the SSS using a bandwidth acquired byscaling down a bandwidth to be transmitted by ½^(m) times and symbols ofa number increased by 2^(m) times based on one symbol may be considered.

For example, as in Method 3 described above, when the default subcarrierspacing of 15 kHz is configured for the center frequency in the vicinityof 4 GHz or 6 GHz, the subcarrier spacing applied to the PSS may beconfigured to 60 kHz (N=4) and the subcarrier spacing applied to the SSSmay be configured to 15 kHz. In this case, when 6 Ribs (i.e., 1.08 MHz,72 resource elements (REs)) are allocated to an SSS sequence (e.g., alegacy SSS sequence) like the existing LTE system, the SSS may betransmitted via one symbol.

In this case, a method for limiting the bandwidth in which the PSS is tobe transmitted to 1.08 MHz and configuring the PSS sequence to betransmitted via four symbols may be considered. A detailed examplethereof is illustrated in FIG. 6.

FIG. 6 illustrates an example of a method for transmitting asynchronized signal to which a method proposed in this specification maybe applied. FIG. 6 is just for convenience of the description and doesnot limit the scope of the present invention.

Referring to FIG. 6, it is assumed that the synchronization signals(i.e., PSS and SSS) are transmitted in accordance with the bandwidth forSSS transmission. Further, it is assumed that the SSS is transmitted ina 5th OFDM symbol (OFDM symbol #5) of the subframe (e.g., a singlesubframe for the SSS numerology) and the PSS is transmitted through fourshort OFDM symbols positioned at a location of a 6th OFDM symbol (OFDMsymbol #6). In this case, since the PSS is transmitted through four OFDMsymbols, the bandwidth for the PSS is ¼ times the existing bandwidth.

In addition, a position (or symbol) at which the SSS and/or the PSSare/is transmitted is merely an example, and the SSS and/or the PSS maybe positioned at an arbitrary symbol which is not overlapped among 14symbols (i.e., OFDM symbols #0 to #13).

The sequence for the PSS transmitted through four OFDM symbols may beconfigured to be transmitted in the same scheme as the followingexamples.

For example, for PSS transmission, four Zadoff-Chu sequences of length17 using different root indexes may be configured to be transmitted oneby one in each symbol. For another example, for PSS transmission, one ZCsequence of length 17 using the same root index may be configured to berepeatedly transmitted to each symbol. For yet another example, for PSStransmission, two ZC sequences (i.e., a first sequence A and a secondsequence B) of length 17 using different root indexes may be generatedand the two generated sequences may be configured to be transmittedthrough four symbols according to various types of combinations such asABAB, AABB, ABBA, etc.

In the above-described PSS transmission schemes, it is advantageous toenhance the correlation performance by applying a cover code to eachsymbol. Further, since the PSS is configured at a subcarrier spacing of60 kHz, it takes only 1 ms to transmit the PSS over four symbols. Inaddition, the PSS and SSS transmission schemes as described above areadvantageous to filter only a predetermined bandwidth (e.g., 1.08 MHz)and receive the synchronization signal even if different subcarrierspacings are configured for the PSS and the SSS.

In this case, the CP scaled down to a subcarrier spacing value (e.g., 60kHz) applied to the PSS may be configured in front of each of the foursymbols.

Further, in various embodiments of the present invention, the samesubcarrier spacing may be configured for the PSS and the SSS, as inMethod 1 and Method 2 described above. In this case, the sequence (i.e.,the PSS sequence) to be used for the PSS may be configured or allocatedthrough the following methods.

First, a method using PSS having the same length as the SSS may beconsidered. That is, the method is a method for configuring the lengthof the SSS sequence and the length of the PSS sequence to be equal toeach other. For example, as described above (e.g., Method 1), when thedefault subcarrier spacing of 15 kHz is configured for the centerfrequency in the vicinity of 4 GHz or 6 GHz, the subcarrier spacingsapplied to the PSS and SSS may be configured to 15 kHz. In this case,when 6 RBs (i.e., 1.08 MHz, 72 REs) are allocated to the PSS and the SSSlike the existing LTE system, (each of) the PSS and the SSS may betransmitted via one symbol.

Next, a method for using a sequence having a length N times shorter thanthe SSS for PSS transmission, but maintaining the existing bandwidthconstant may be considered. In this case, the existing bandwidth may bemaintained constant by mapping the PSS sequence every N REs instead ofmapping the PSS sequence to the RE on a frequency axis. That is, even ifthe PSS sequence is shorter than the SSS sequence, the transmissionbandwidths of the PSS and SSS may be maintained to be equal to eachother by mapping the PSS sequence at regular intervals. In this case,‘0’ may be filled in a subcarrier (or RE) to which the PSS sequence isnot mapped and the subcarrier to which the PSS sequence is mapped may betransmitted using power increased by N times. A detailed example thereofis illustrated in FIGS. 7A and 7B.

FIGS. 7A and 7B illustrate another example of the method fortransmitting the synchronized signal to which the method proposed inthis specification may be applied. FIGS. 7A and 7B are just forconvenience of the description and does not limit the scope of thepresent invention.

Specifically, FIG. 7A illustrates the existing PSS sequence mappingscheme and FIG. 7B illustrates a PSS sequence mapping scheme proposed inthis specification.

Referring to FIGS. 7A and 7B, each square means the subcarrier (or RE),and the checked region means an RE to which the PSS sequence is mapped.Further, it is assumed that the length of the PSS sequence proposed inthis specification is configured to be N times shorter than that of theexisting PSS sequence.

In the case of FIG. 7A, as described above, the existing PSS sequencemay be configured to be mapped to every RE and the subcarrier spacingmay be expressed by Fd kHz.

In contrast, in the case of FIG. 7B, the PSS sequence proposed in thisspecification may be configured to be mapped to every N REs. In thiscase, a spacing between subcarriers (i.e., the subcarriers to which thePSS sequence is mapped) to which ‘0’ is not mapped may be expressed asN*Fd kHz. Further, on a time axis, the same sequence is repeated N timesin a space within one symbol excluding the CP length, and as a result,an actual symbol duration is not changed. As an example, when the PSSsequence is mapped to every RE, a time duration corresponding to the PSSsequence may be configured to be equal to a symbol duration. In thiscase, when the PSS sequence is mapped to every N REs, the time durationcorresponding to the PSS sequence may be 1/N times the symbol duration.Accordingly, when the PSS sequence is mapped to every N REs, the PSSsequence may be repeated N times for the same symbol duration.

Using the PSS sequence configuring and allocating method (e.g., themethod illustrated in FIG. 7B) proposed in this specification, when theUE performs frequency estimation (or frequency measurement) using thePSS, the UE may be less affected by the carrier frequency offset.Specifically, when the PSS is mapped to every REs according to theexisting scheme (e.g., FIG. 7A), the inter-cell interference (ICI) dueto adjacent subcarriers may be large depending on the influence of thecarrier frequency offset. On the other hand, when the PSS is mapped andtransmitted for every N REs as proposed in this specification, there isthe inter-cell interference due to subcarriers spaced apart byN*subcarrier spacing, so that the influence may be reduced.

Further, regarding a cell ID (e.g., a physical layer cell ID), in theexisting case, a method is used, in which one of three PSS sequencecandidates and one of 168 SSS sequence candidates are selected to select(or identify or determine) one of 504 cell identifiers. However, in theabove method, in order to distinguish three candidates for selecting thePSS, the UE needs to repeatedly perform operations with high complexitythree times.

Accordingly, in order to reduce a burden of the UE, a method forselecting one of the cell identifiers by using one candidate for the PSSand using candidates corresponding to the total number of cellidentifiers for the SSS may be considered. As an example, a method forusing one candidate for the PSS and using 504 or 1008 candidates for theSSS may be considered.

In this case, since the method reduces the number of candidates inrelation to the PSS, the PSS sequence(s) of the above-described schememay be used as it is. As an example, the PSS sequence may be generatedusing Equations 3, 4, and 5 described above.

However, since the number of candidates increases for the SSS, a designmethod for the SSS sequence needs to be newly considered. That is, amethod for generating (or configuring) the SSS sequences as many as allcell identifiers needs to be considered. As an example, the PSS sequencemay be generated using Equations 6, 7, and 8 described above.

Specifically, the SSS may be configured (or designed, allocated) in thefollowing scheme in order to distinguish all cell identifiers (e.g., 504cell identifiers, 1008 cell identifiers). Hereinafter, for convenienceof the description, it is assumed that the total number of cellidentifiers is configured to 504 which is the total number of cellidentifiers in the existing LTE system. In this case, it is needless tosay that the corresponding method may be similarly applied even to thecase where the total number of cell identifiers of the NR system isdifferent from the existing case (e.g., 1008).

For example, a total length 72 sequence may be used for the SSSsequence, but a length 67 sequence may first be generated inconsideration of a guard region. That is, by considering the guardregion, a sequence may be used, which has a shorter length than thefrequency domain allocated to the SSS sequence may be used. Here, thetotal length 72 may also be used when the bandwidth is 1.04 MHz, thesubcarrier spacing is 15 kHz and/or the bandwidth is 4.16 MHz and thesubcarrier spacing is 60 kHz. In this case, the generated length 67sequence may be a ZC sequence (Zadoff-Chu sequence), an M sequence (Msequence), or the like.

Thereafter, a length 68 sequence (e.g., a ZC sequence, an M sequence,etc.) may be generated by adding one sample to the generated length 67sequence. For example, the length 68 sequence may be generated by adding(i.e., cyclically shifting) first one sample of the sequence to the endof the sequence. Alternatively, as another example, a method forgenerating the length 68 sequence by adding ‘0 (zero)’ to an arbitrarydigit may be considered. In this case, the method (that is, the methodusing the cyclic shift) of the first example may be more advantageous.

Thereafter, a sequence of total length 72 may be generated by adding twosamples of ‘0’ to be used for guarding at both ends of the generatedlength 68 sequence. In other words, the sequence used for the generationof the SSS sequence may be generated (or configured, designed) accordingto the length of the resource region allocated to the SSS sequencetransmission. Hereinafter, in this specification, the sequence generatedthrough the above procedures may be referred to as a first sequence.

When the generated length 72 sequence is the ZC sequence, a total of 67root indexes may be used for the corresponding sequence. However, only63 root indexes (e.g., 3, 4, 5, . . . , 63, 64, 65) out of 67 rootindexes may be used in consideration of the Peak-to-Average Power Ratio(PAPR). Alternatively, when the generated length 72 sequence is based onan M sequence of length 68, the sequence may utilize a total of 68cyclic shift values. Even in this case, only some cyclic shift values(e.g., 63 values) may be used in consideration of the PAPR and thecorrelation value.

In this case, a scrambling sequence to be applied to the sequencegenerated through the above-described procedures may be additionallyconsidered. Here, the scrambling sequence may mean a sequence multipliedby a specific sequence. That is, in order to generate the SSS sequence,a method for multiplying the generated sequence by a sequence having thesame length as the corresponding sequence may be considered. In thiscase, a product between the sequences may mean a product between eachelement (or sample) of the sequence corresponding to the same position.For example, when the first sequence is constituted by [0 1 1 1 0 . . .] and the second sequence is constituted by [0 0 1 1 1 . . . ], asequence generated by the product of the elements of two sequences is[0*0 1*0 1*1 1*1 0*1 . . . ].

In this case, the scrambling sequence may be a pseudo-random noisesequence (PN sequence), an M sequence, a Hadamard sequence, a binarysequence, or the like.

For example, when the PN sequence is used as the scrambling sequence, amethod may be considered, in which a PN sequence of length 63 isgenerated with a scrambling sequence for a sequence of length 68 (e.g.,a ZC sequence of length 68) as described above and then, a PN sequenceof length 68 is generated by adding 5 samples. Even in this case, in thesame scheme as described above, a method for adding 5 samples at thebeginning of the sequence to the end of the sequence (i.e., cyclicshift) or generating the length 68 sequence by adding ‘0 (zero)’ to anarbitrary digit five times may be considered.

In this case, in order for the scrambling sequences to have eightcandidates, the sequence may be cyclically shifted using a specificstarting sample value (or a specific initial value). Alternatively, amethod of using eight different PN sequences by configuring differentseed values for generating the PN sequence may also be considered. Thetwo methods are different from each other in that in the former, thesame (i.e., single) sequence is cyclically shifted and used in eightdifferent forms and in the latter, eight different sequences are used.

Alternatively, as another example, when the M sequence is used as thescrambling sequence, a method for generating an M sequence of length 68as the scrambling sequence for the length 68 sequence (e.g., a ZCsequence of length 68, an M sequence of length 68) described above maybe considered. In this case, the eight candidates may be separated (orgenerated) by eight different cyclic shift values so that the scramblingsequences have eight candidates.

Thereafter, a sequence of total length 72 may be generated by adding twosamples of ‘0’ to be used for guarding at both ends of the generatedlength 68 sequence. Hereinafter, in this specification, the sequencegenerated through the above procedures may be referred to as a secondsequence.

Through the procedures described above, two length 72 sequences, i.e., aspecific sequence (i.e., the first sequence) and the scrambling sequence(i.e., the second sequence) for the specific sequence may be generatedand the SSS sequence may be finally generated by scrambling twogenerated sequences. For example, the SSS sequence may be generated byscrambling the PN sequence of length 72 for the ZC sequence of length72. Alternatively, as another example, the SSS sequence may be generatedby scrambling another M sequence of length 72 for the M sequence oflength 72.

In this case, when the number of candidates for the specific sequence(i.e., the first sequence) is configured to 63 and the number ofcandidates for the scrambling sequence (i.e., the second sequence) isconfigured to 8, a total of 63*8, i.e., 504 SSS sequence candidates maybe separated (or distinguished). Accordingly, when the total number ofcell identifiers is 504, the SSS sequences may be generated as many asall cell identifiers.

As mentioned above, it is needless to say that the above-described SSSsequence configuration (or generation) scheme may be applied even if thenumber of cell identifiers is configured to a number other than 504. Forexample, when the number of cell identifiers is configured to 1008 inthe NR system, 112 candidates for the first sequence may be configuredand 9 candidates for the second sequence may be configured. In thiscase, the number of SSS sequence candidates that may be finallygenerated through the product (i.e., the product between the elements ofthe first sequence and the elements of the second sequence) between thefirst sequence and the second sequence is 1008. Further, in this case,as the sequence length for the synchronization signal becomes longer,the number of frequency domains allocated to the synchronization signal,that is, the number of RBs may be increased (e.g., 12 RBs).

In this case, the length of the first sequence and the length of thesecond sequence are configured to be equal to each other and the lengthof the first sequence and the length of the second sequence are equal tothe length of the finally formed SSS sequence. That is, the actualsequence length excluding the guard region in the first sequence and thesecond sequence is equal to the length of the actual SSS sequence exceptfor the guard region.

Further, in this regard, in the existing LTE system, interleaving twoshort sequences (e.g., length 31 sequences) to configure (or generate)the SSS sequence, while the SSS sequence proposed in this specificationis configured based on a long sequence. Here, the long sequence may meana sequence not generated by interleaving a plurality of sequences.Alternatively, the long sequence may mean a sequence (or some sequencesconfigured to have a short length considering the guard region)configured in accordance with the resource region allocated to the SSSsequence. When the SSS sequence is generated (or configured) using thelong sequence rather than the short sequence, the cross correlationperformance between the sequences is enhanced, and as a result, a ghosteffect in which the UE does not receive the SSS may be prevented.

Further, as described above, the number of candidates of the firstsequence and the number of candidates of the second sequence may beconfigured to be uneven (i.e., the number of candidates of a part may beconfigured to be larger than the number of candidates of another part).When the number of candidates in the first sequence and the number ofcandidates in the second sequence are configured to be equal to eachother, the cross correlation value between the SSS sequences generatedusing the first sequence and the second sequence may be large (e.g.,0.5). In contrast, when the number of candidates of the first sequenceand the number of candidates of the second sequence are configured to beunequal, the cross correlation value between the generated SSS sequencesis small (i.e., the cross correlation performance is good). Therefore,when the number of candidates of the first sequence is configured to bedifferent from the number of the candidates of the second sequence,there is an advantage that the detection performance of the SSSsequence, that is, the SSS may be enhanced.

Further, when the first sequence and the second sequence are the Msequences, the PSS sequence may be generated based on a first polynomialused for generating the first sequence or a second polynomial used forgenerating the second sequence. In this case, as the polynomial forgenerating the PSS sequence is overlapped with any of the polynomialsfor generating the SSS sequence, the complexity for generating thesequence for the synchronization signal may be lowered.

Further, as the initial values and/or polynomials for generating the SSSsequence as described above, the values and/or equations of thesynchronization signal related contents described above may be used.

Further, in order to distinguish a subframe index and/or a frame indexusing the SSS, a method for additionally applying another scramblingsequence (that is, a third sequence) to the SSS (i.e., SSS sequence)generated through the above-described procedures may also be considered.That is, the number of candidates may be increased by additionallyapplying another scrambling sequence and the subframe index and/or theframe index may be configured to be distinguished through a newlyconfigured candidate.

FIG. 8 illustrates yet another example of the method for transmittingthe synchronization signal to which the method proposed in thisspecification may be applied. FIG. 8 is merely for convenience of thedescription and does not limit the scope of the present invention.

Referring to FIG. 8, it is assumed that the subcarrier spacing appliedto the PSS is configured to be four times larger than the subcarrierspacing applied to the SSS, and the subcarrier spacing applied to thePBCH is configured to be equal to the subcarrier spacing applied to theSSS. It is also assumed that two kinds of ZC sequences (ZC sequence ofroot index 7 and ZC sequence of root index 10) with different rootindexes are used for PSS transmission. For example, two ZC sequenceswith length 17 using different root indexes are used for transmission ofthe PSS.

In this case, the PSS is transmitted through four ZC sequences withlength 17 in which the ZC sequence corresponding to each root index isrepeated twice.

In this case, a transmission bandwidth of the PSS is configured the sameas the transmission bandwidth of the SSS, and a cover code of [1, 1, −1,1] may be applied to the PSS, i.e., four ZC sequences with length 17. Inaddition, zero padding for a guard region may be performed at one end ofthe PSS and at both ends of the SSS. In this case, the PSS istransmitted through four symbols (in this case, the time durationcorresponding to all four symbols is the same as one symbol durationconfigured according to the subcarrier duration of the SSS). Further, asillustrated in FIG. 8, the root index used in the PSS sequence may beallocated to [7, 10, 7, 10].

Further, in this case, as illustrated in FIG. 8, a CP length for SSStransmission and a CP length for PBCH transmission may be configured tobe the same as each other. In addition, the length of the substantialSSS sequence may be configured to be smaller than the length of the PBCHsequence (i.e., the sequence used for PBCH transmission).

Further, in the above-described SSS sequence generation (orconfiguration) scheme, a default subcarrier spacing value is configuredto 15 kHz. However, this is only an example for convenience ofdescription, and the default subcarrier spacing may be 30 kHz, 60 kHz,etc. in a band of 6 GHz or less, and may be 120 kHz, 240 kHz, etc. aswell as 60 kHz in a band of 6 GHz or more. Thus, based on the defaultsubcarrier spacing value, the subcarrier spacing value used for the PSSand/or SSS may be scaled to be larger or smaller according to themethods described above.

Further, in various embodiments of the present invention, like Method 1and Method 2 described above, the following PSS sequence configuringand/or allocating method may be considered when the same subcarrierspacing is configured for the PSS and the SSS. Hereinafter, forconvenience of description, it is assumed that the subcarrier spacingsapplied to the PSS and the SSS are 15 kHz.

For example, a method of transmitting a PSS sequence (i.e., a sequencefor PSS) by frequency division multiplexing (FDM) four ZC symbols withlength 17 using different root indexes into one symbol may beconsidered. As another example, a method of transmitting a PSS sequenceby FDM of one ZC sequence with length 17 using the same root index toone symbol may be considered. In another example, a method of generatingtwo ZC sequences (i.e., a first sequence A, a second sequence B) withlength 17 using different root indexes and transmitting a PSS sequenceby FDM of the two sequences generated in various combinations such asABAB, AABB, and ABBA through four symbols may be considered.

In the above examples, it is advantageous to apply a cover code for eachZC sequence(s) to improve correlation performance.

In this case, the above-described PSS may have one or three sequencecandidates for detecting a cell identifier. When there are three PSSsequence candidates, different root indexes need to be configuredaccording to the above-described method for each candidate. On the otherhand, when there is one PSS sequence candidate, the SSS sequence may begenerated (or configured) based on a scheme (that is, a scheme in whichthe total number of candidates of the SSS sequence is configured to beequal to the total number of cell identifiers) for identifying all cellidentifiers.

FIG. 9 illustrates still yet another example of the method fortransmitting the synchronization signal to which the method proposed inthis specification may be applied. FIG. 9 is just for convenience of thedescription and does not limit the scope of the present invention.

Referring to FIG. 9, it is assumed that two kinds of ZC sequences (ZCsequence of root index 7 and ZC sequence of root index 10) withdifferent root indexes are used for PSS transmission. Here, the lengthof the ZC sequence is configured to 17.

Four ZC sequences (that is, two are used for one kind of ZC sequence) ismapped to a resource region through the FDM method as described above.In this case, the cover code [1, 1, −1, 1] may be applied to the PSS,i.e., four ZC sequences. In addition, zero padding for a guard regionmay be performed at one end of the PSS and at both ends of the SSS.Further, as illustrated in FIG. 9, the root index for FDM sequences withlength 17 may be configured to [7, 10, 7, 10].

Further, with respect to the PSS sequence as described above, the rootindex (i.e., the root index for generation of ZC sequences) for the ZCsequences may be selected to have a complex conjugate relation betweenthe generated ZC sequences. That is, when the length of the ZC sequenceis N_(ZC), the ZC sequence can be selected by a combination of(N_(ZC)−1)/2−m and (N_(ZC)−1)/2+m+1. Here, m means an integer largerthan 0 and smaller than (N_(ZC)−1)/2, including 0. Such a route indexselection method may be applied regardless of a duplex mode of the PSSdesign.

Further, in FIG. 8 described above, with respect to the PSS, adown-scaled CP is configured for each OFDM symbol having a subcarrierspacing of 60 kHz. Unlike this (that is, the down-scaled CP is notattached to each OFDM symbol), a method of generating one CP (i.e., asingle CP) corresponding to the CP length used for an OFDM symbol with asubcarrier spacing of 15 kHz and attaching (or configuring) thegenerated one CP to the front portion of the four OFDM symbols may beconsidered. An example thereof is illustrated in FIG. 10.

FIG. 10 illustrates still yet another example of the method fortransmitting the synchronization signal to which the method proposed inthis specification may be applied. FIG. 10 is merely for convenience ofexplanation and does not limit the scope of the present invention.

Referring to FIG. 10, it is assumed that two kinds of ZC sequences (ZCsequence of root index 7 and ZC sequence of root index 10) withdifferent root indexes are used for PSS transmission. Here, the lengthof the ZC sequence is configured to 17.

In this case, the PSS is transmitted through four symbols correspondingto a subcarrier spacing of 60 kHz, and in this case, no CP period isallocated between the four symbols. Instead, a CP corresponding to thesubcarrier spacing of 15 kHz is located in front portion of fourconsecutive symbols.

Through such arrangement (i.e., arrangement in which the CP length andthe location are matched to those of the default subcarrier spacing), itis advantageous to support multiplexing with a data signal transmittedin another band in which the PSS is not transmitted. Here, the PSS isconfigured to use a subcarrier spacing (e.g., a subcarrier spacing of 60kHz) corresponding to N times (for example, N=4) of the defaultsubcarrier spacing, and the data signal may be configured to use adefault subcarrier spacing (for example, 15 kHz).

In addition, the method of generating the above-described model may bedescribed as follows. That is, in the case where the CP lengthcorresponding to the default subcarrier spacing is used for thesynchronization signal (e.g., PSS) using the subcarrier spacingcorresponding to N times the default subcarrier spacing, thesynchronization signal configuration (or a synchronization signalmapping method) may also be performed as illustrated in the followingexample. In this case, it is assumed that first N OFDM symbols arerepeatedly configured.

For example, for a single OFDM symbol configured at the defaultsubcarrier spacing (e.g., 15 kHz), a comb type symbol may be generatedby mapping information is mapped to every N REs based on a frequencydomain and inserting 0 to the remaining N−1 REs. Thereafter, a timedomain sequence of N_(IFFT)/N length may be generated (obtained) bydividing a time domain sequence generated by performing inverse fastFourier transform (IFFT) with an N_(IFFT) size into N equal parts.

In this case, as illustrated in FIG. 9, in order to obtain the sameeffect as using the root index value having a complex conjugaterelation, in a region of the first N_(IFFT)/N length (i.e., the firstsymbol of the N OFDM symbols), the N-divided time domain sequence isinserted, and in a next region of N_(IFFT)/N length, a time domainsequence configured as the complex conjugate value of the N-divideddomain sequence may be inserted. The above operation is repeated untilthe length becomes N_(IFFT), so that a final time domain sequence may begenerated. That is, finally, the above-described operation may berepeated until a time-domain sequence of the N_(IFFT)/N length isgenerated.

Thereafter, by inserting (attaching) one (i.e., single) CP correspondingto the CP length used in the OFDM symbol having the default subcarrierspacing to the front part of the symbols to which the corresponding timedomain sequence is mapped, the final time domain OFDM symbol (i.e., thefinal time domain OFDM symbol structure) may be completed.

Substituting a specific number for the above example is as follows. When1.08 MHz is used as the transmission bandwidth of the synchronizationsignal and 4 repetitions are considered for 72 REs, a ZC sequence withlength 17 is inserted to every 4 REs and ‘0’ may be inserted to theremaining three REs. Here, length 17 may mean a length corresponding tothe largest odd number among the numbers smaller than or equal to avalue (i.e., 18) obtained by dividing 72 by 4.

Thereafter, IFFT is performed with 512 IFFT sizes, and a time domainsequence with length 128 may be obtained by dividing length 512 into 4equal parts. Thereafter, the four-divided time domain sequence isinserted to the first 128-length region (i.e., the first region where a128-length time domain sequence may be mapped, that is, the first OFDMsymbol of 4 OFDM symbols), and a time domain sequence configured as thecomplex conjugate value of the four-divided time domain sequence may beinserted to a next region. By repeating such an operation twice more, atime domain sequence of a total length of 512 may be generated.Thereafter, a final time domain OFDM symbol may be completed byinserting a CP with length 40 or 36.

Alternatively, as another example, for an OFDM symbol using a subcarrierspacing scaled by N times of the default subcarrier spacing (e.g., 15kHz), a method of generating the above-described model by inserting datato each RE based on a frequency domain may be considered. After the datais inserted to each RE, a time domain sequence with a length ofN_(IFFT)/N may be generated (obtained) by performing inverse fastFourier transform (IFFT) with an N_(IFFT)/N size.

In this case, as illustrated in FIG. 9 above, in order to obtain thesame effect as using the root index value having a complex conjugaterelation, in a region of the first N_(IFFT)/N length, the generated(i.e., first generated) time domain sequence is inserted, and in a nextregion of N_(IFFT)/N length, a time domain sequence configured as thecomplex conjugate value of the generated time domain sequence may beinserted. The above operation is repeated until the length becomesN_(IFFT), so that a final time domain sequence may be generated. Thatis, finally, the above-described operation may be repeated until a timedomain sequence of the N_(IFFT)/N length is generated.

Thereafter, by inserting one CP corresponding to the CP length used inthe OFDM symbol having the default subcarrier spacing to the front partof the symbols to which the corresponding time domain sequence ismapped, the final time domain OFDM symbol (i.e., the final time domainOFDM symbol structure) may be completed.

Substituting a specific number for the above example is as follows. When1.08 MHz is considered as the transmission bandwidth of thesynchronization signal, a ZC sequence configured with length 17 isinserted (or mapped) to 18 REs and ‘0’ may be inserted to the remainingone RE. In this case, it is assumed that 17 is selected as the oddlength.

Thereafter, an IFFT is performed with a 128 IFFT size, so that a128-length time domain sequence may be obtained. Thereafter, thegenerated time domain sequence is directly inserted into the first128-length region (i.e., the first region in which a 128-length timedomain sequence may be mapped), and a time domain sequence configuredwith the complex conjugate value of the generated sequence may beinserted to a next region thereof. By repeating such an operation twicemore, a time domain sequence of a total length of 512 may be generated.Thereafter, a final time domain OFDM symbol may be completed byinserting a CP with length 40 or 36.

Further, the cover code used in the methods proposed in thisspecification may be configured in the same form as in the case of notapplying the cover code such as [1, 1, 1, 1].

In addition, in the methods proposed in this specification, by assuminga case where the sync bandwidth (i.e., a transmission bandwidth for asynchronous signal) is about 1 MHz (i.e., 1.08 MHz), a length (i.e., alength of a sequence) is configured. However, this is just forconvenience of explanation, and it is natural that even if the syncbandwidth increases to K MHz, the above-described methods may be appliedby extending (that is, scalably adjusting) the length of the sequence byL times. For example, even when the sync bandwidth is configured toabout 5 MHz (e.g., 4.32 MHz), the length of the sequence is configuredto be 4 times longer (i.e., 4.32/1.08=4 times), and thus the methodsproposed in this specification may be applied in the same manner.

Further, the methods proposed in this specification may be applied notonly below 6 GHz band but also above 6 GHz band (e.g., 30 GHz, 40 GHz,etc.). In addition, a default numerology may be represented by areference numerology, a numerology used in a specific frequency band,and the like. In addition, even if the default numerology is changed,the length of the sequence is constant and has a scalable transmissionbandwidth in accordance with the subcarrier spacing.

FIG. 11 illustrates an operation flowchart of a user equipment whichperforms synchronization through transmission and reception of asynchronization signal to which a method proposed in this specificationmay be applied. FIG. 11 is merely for convenience of the description anddoes not limit the scope of the present invention.

Referring to FIG. 11, it is assumed that the UE monitors asynchronization signal at a pre-configured bandwidth with respect to asynchronization signal.

In step S1105, the UE receives a PSS and an SSS from the base station.In this case, the PSS and the SSS may be received by the methoddescribed above. That is, the UE receives the PSS and the SSS usingresource elements to which the sequence (i.e., the PSS sequencedescribed above) for the PSS is mapped and resource elements to whichthe sequence (i.e., the SSS sequence described above) for the SSS ismapped. In this case, the sequence for the PSS and the sequence for theSSS may be generated (or configured) according to the above-describedmethod(s).

In this case, the sequence for the SSS is generated by a product betweena first sequence and a second sequence. Here, the number (i.e., thenumber of candidates of the first sequence that may be used forgenerating the SSS sequence) of the first sequences is larger than thenumber (i.e., the number of candidates of the second sequence that maybe used for generating the SSS sequence) of the second sequences.

In addition, the number (i.e., the number of generable SSS sequences,the number of candidates of the SSS sequences) of sequences for the SSSmay be configured to be equal to the number (e.g., 1008) of cellidentifiers (e.g., physical layer cell identifiers). In this case, thenumber of the cell identifiers may be configured to be equal to theproduct of the number of the first sequences and the number of thesecond sequences.

In addition, the product between the first sequence and the secondsequence may be a product between each element of the first sequence andeach element of the second sequence, as described above.

Further, as described above, the length of the first sequence and thelength of the second sequence may be the same as the length of thesequence for the SSS, respectively. That is, the SSS sequence may begenerated by a product of two sequences (i.e., a long sequence) havingthe same length as the SSS sequence. In this case, any one of the firstsequence and the second sequence may be an M sequence (m sequence). Inthis case, the M sequence may be generated based on a specific initialvalue (e.g., [0 0 0 0 0 0 1]) and a specific cyclic shift. That is, theM sequence may be generated using a polynomial having a specific initialvalue and a cyclic shift satisfying a predetermined condition.

In addition, the polynomial for the sequence for the PSS may beconfigured to be equal to either a first polynomial for the firstsequence or a second polynomial for the second sequence. For example,when the polynomials for generating the SSS sequence are represented byx₀(n) and x₁(n), and the polynomial for generating the PSS sequence isrepresented by x(n), x(n) may be configured to be equal to x₀(n).However, even in this case, as described above, the initial values ofthe polynomials may be configured to be different from each other.

Further, as illustrated in FIG. 8, the SSS is received contiguously witha physical broadcast channel (PBCH), and the CP applied to the SSS andthe CP applied to the PBCH may be configured to be the same as eachother.

Overview of Devices to which Present Invention is Applicable

FIG. 12 illustrates a block diagram of a wireless communication deviceto which methods proposed in this specification may be applied.

Referring to FIG. 12, a wireless communication system includes a basestation 1210 and multiple UEs 1210 positioned within an area of the basestation 1220.

The base station 1210 includes a processor 1211, a memory 1212, and aradio frequency (RF) unit 1213. The processor 1211 implements afunction, a process, and/or a method which are proposed in FIGS. 1 to 11above. The layers of the wireless interface protocol may be implementedby the processor 1211. The memory 1212 is connected with the processor1211 to store various pieces of information for driving the processor1211. The RF unit 1213 is connected with the processor 1211 to transmitand/or receive a radio signal.

The UE 1220 includes a processor 1221, a memory 1222, and an RF unit1223.

The processor 1221 implements a function, a process, and/or a methodwhich are proposed in FIGS. 1 to 11 above. The layers of the wirelessinterface protocol may be implemented by the processor 1221. The memory1222 is connected with the processor 1221 to store various pieces ofinformation for driving the processor 1221. The RF unit 1223 isconnected with the processor 1221 to transmit and/or receive a radiosignal.

The memories 1212 and 1222 may be positioned inside or outside theprocessors 1211 and 1221 and connected with the processors 1211 and 1221by various well-known means.

As an example, in a wireless communication system supporting a lowlatency service, the UE may include a radio frequency (RF) unit fortransmitting and receiving a radio signal and a processor functionallyconnected with the RF unit in order to transmit and receive downlink(DL) data.

Further, the base station 1210 and/or the UE 1220 may have a singleantenna or multiple antennas.

FIG. 13 illustrates a block diagram of a communication device accordingto an embodiment of the present invention.

In particular, FIG. 13 is a diagram more specifically illustrating theUE of FIG. 8 above.

Referring to FIG. 13, the UE may be configured to include a processor(or a digital signal processor (DSP) 1310, an RF module (or RF unit)1335, a power management module 1305, an antenna 1340, a battery 1355, adisplay 1315, a keypad 1320, a memory 1330, a subscriber identificationmodule (SIM) card 1325 (this component is optional), a speaker 1345, anda microphone 1350. The UE may also include a single antenna or multipleantennas.

The processor 1310 implements a function, a process, and/or a methodwhich are proposed in FIGS. 1 to 11 above. Layers of a wirelessinterface protocol may be implemented by the processor 1310.

The memory 1330 is connected with the processor 1310 to storeinformation related to an operation of the processor 1310. The memory1330 may be positioned inside or outside the processor 1310 andconnected with the processor 1310 by various well-known means.

A user inputs command information such as a telephone number or the likeby, for example, pressing (or touching) a button on the keypad 1320 orby voice activation using the microphone 1350. The processor 1310receives such command information and processes to perform appropriatefunctions including dialing a telephone number. Operational data may beextracted from the SIM card 1325 or the memory 1330. In addition, theprocessor 1310 may display command information or drive information onthe display 1315 for the user to recognize and for convenience.

The RF module 1335 is connected with the processor 1310 to transmitand/or receive an RF signal. The processor 1310 transfers the commandinformation to the RF module 1335 to initiate communication, forexample, to transmit radio signals constituting voice communicationdata. The RF module 1335 is constituted by a receiver and a transmitterfor receiving and transmitting the radio signals. The antenna 1340functions to transmit and receive the radio signals. Upon receiving theradio signals, the RF module 1335 may transfer the signal for processingby the processor 1310 and convert the signal to a baseband. Theprocessed signal may be converted into to audible or readableinformation output via the speaker 1345.

The aforementioned embodiments are achieved by a combination ofstructural elements and features of the present disclosure in apredetermined manner. Each of the structural elements or features shouldbe considered selectively unless specified separately. Each of thestructural elements or features may be carried out without beingcombined with other structural elements or features. In addition, somestructural elements and/or features may be combined with one another toconstitute the embodiments of the present disclosure. The order ofoperations described in the embodiments of the present disclosure may bechanged. Some structural elements or features of one embodiment may beincluded in another embodiment, or may be replaced with correspondingstructural elements or features of another embodiment. Moreover, it isapparent that some claims referring to specific claims may be combinedwith another claims referring to the other claims other than thespecific claims to constitute the embodiment or add new claims by meansof amendment after the application is filed.

The embodiments of the present disclosure may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present disclosure may be achieved by one or moreASICs (Application Specific Integrated Circuits), DSPs (Digital SignalProcessors), DSPDs (Digital Signal Processing Devices), PLDs(Programmable Logic Devices), FPGAs (Field Programmable Gate Arrays),processors, controllers, microcontrollers, microprocessors, etc.

In a firmware or software configuration, the embodiments of the presentdisclosure may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in the memory and executed bythe processor. The memory may be located at the interior or exterior ofthe processor and may transmit data to and receive data from theprocessor via various known means.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present disclosurewithout departing from the spirit or scope of the inventions. Thus, itis intended that the present disclosure covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

Although a scheme of transmitting and receiving a synchronization signalin a wireless communication system of the present invention has beendescribed with reference to an example applied to a 3GPP LTE/LTE-Asystem or a 5G system (New RAT system), the scheme may be applied tovarious wireless communication systems in addition to the 3GPP LTE/LTE-Asystem or 5G system.

What is claimed is:
 1. A method of transmitting a synchronization signalby a base station in a wireless communication system, the methodcomprising: determining a sequence for a primary synchronization signal(PSS); determining a sequence for a secondary synchronization signal(SSS); and transmitting, to a user equipment (UE), the PSS and the SSSbased on the sequence for the PSS and the sequence for the SSS, whereinthe sequence for the SSS is generated based on a product of a firstsequence and a second sequence, wherein a length of the sequence for theSSS is configured to be equal to a length of the first sequence and alength of the second sequence, wherein a number of candidates of thefirst sequence is configured to be larger than a number of candidates ofthe second sequence, wherein a product of the number of candidates ofthe first sequence and the number of candidates of the second sequenceis identical to a number of cell identifiers supported by the wirelesscommunication system, wherein a subcarrier spacing for the PSS and asubcarrier spacing for the SSS are based on any one of a plurality ofsubcarrier spacings supported by the wireless communication system, andwherein a subcarrier spacing for a Physical Broadcast channel (PBCH)that is related to the PSS and the SSS is configured to be equal to thesubcarrier spacing for the PSS and the subcarrier spacing of the SSS. 2.The method of claim 1, wherein the product of the first sequence and thesecond sequence comprises pairwise products of elements of the firstsequence and the second sequence.
 3. The method of claim 1, wherein anyone of the first sequence and the second sequence is an M sequence. 4.The method of claim 3, wherein the M sequence is generated based on aspecific initial value and a specific cyclic shift.
 5. The method ofclaim 1, wherein a polynomial for the sequence for the PSS is configuredto be equal to any one of a first polynomial for the first sequence anda second polynomial for the second sequence.
 6. The method of claim 5,wherein: based on the polynomial for the sequence for the PSS beingx(n): x(0) is 0, x(1) is 1, x(2) is 1, x(3) is 0, x(4) is 1, x(5) is 1,and x(6) is 1, based on the first polynomial being x₀(n): x₀(0) is 1,x₀(1) is 0, x₀(2) is 0, x₀(3) is 0, x₀(4) is 0, x₀(5) is 0, and x₀(6) is0, and based on the second polynomial being x₁(n): x₁(0) is 1, x₁(1) is0, x₁(2) is 0, x₁(3) is 0, x₁(4) is 0, x₁(5) is 0, and x₁(6) is
 0. 7.The method of claim 1, wherein a symbol in which the SSS is transmittedis contiguous in time to a symbol in which the PBCH is transmitted.
 8. Abase station configured to transmit a synchronization signal in awireless communication system, the base station comprising: at least onetransceiver; at least one processor; and at least one computer memoryoperably connected to the at least one processor and storinginstructions that, based on being executed by the at least oneprocessor, perform operations comprising: determining a sequence for aprimary synchronization signal (PSS); determining a sequence for asecondary synchronization signal (SSS); and transmitting, to a userequipment (UE) via the at least one transceiver, the PSS and the SSSbased on the sequence for the PSS and the sequence for the SSS, whereinthe sequence for the SSS is generated based on a product of a firstsequence and a second sequence, wherein a length of the sequence for theSSS is configured to be equal to a length of the first sequence and alength of the second sequence, wherein a number of candidates of thefirst sequence is configured to be larger than a number of candidates ofthe second sequence, wherein a product of the number of candidates ofthe first sequence and the number of candidates of the second sequenceis identical to a number of cell identifiers supported by the wirelesscommunication system, wherein a subcarrier spacing for the PSS and asubcarrier spacing for the SSS are based on any one of a plurality ofsubcarrier spacings supported by the wireless communication system, andwherein a subcarrier spacing for a Physical Broadcast channel (PBCH)that is related to the PSS and the SSS is configured to be equal to thesubcarrier spacing for the PSS and the subcarrier spacing of the SSS. 9.The base station of claim 8, wherein the product of the first sequenceand the second sequence comprises pairwise products of elements of thefirst sequence and the second sequence.
 10. The base station of claim 8,wherein any one of the first sequence and the second sequence is an Msequence.
 11. The base station of claim 10, wherein the M sequence isgenerated based on a specific initial value and a specific cyclic shift.12. The base station of claim 8, wherein a polynomial for the sequencefor the PSS is configured to be equal to any one of a first polynomialfor the first sequence and a second polynomial for the second sequence.13. The base station of claim 12, wherein: based on the polynomial forthe sequence for the PSS being x(n): x(0) is 0, x(1) is 1, x(2) is 1,x(3) is 0, x(4) is 1, x(5) is 1, and x(6) is 1, based on the firstpolynomial being x₀(n): x₀(0) is 1, x₀(1) is 0, x₀(2) is 0, x₀(3) is 0,x₀(4) is 0, x₀(5) is 0, and x₀(6) is 0, and based on the secondpolynomial being x₁(n): x₁(0) is 1, x₁(1) is 0, x₁(2) is 0, x₁(3) is 0,x₁(4) is 0, x₁(5) is 0, and x₁(6) is
 0. 14. The base station of claim 8,wherein a symbol in which the SSS is transmitted is contiguous in timeto a symbol in which the PBCH is transmitted.
 15. A processing deviceconfigured to control a base station to transmit a synchronizationsignal in a wireless communication system, the processing devicecomprising: at least one processor; and at least one memory operablyconnected to the at least one processor and storing instructions that,based on being executed by the at least one processor, performoperations comprising: determining a sequence for a primarysynchronization signal (PSS); determining a sequence for a secondarysynchronization signal (SSS); and transmitting, to a user equipment(UE), the PSS and the SSS based on the sequence for the PSS and thesequence for the SSS, wherein the sequence for the SSS is generatedbased on a product of a first sequence and a second sequence, wherein alength of the sequence for the SSS is configured to be equal to a lengthof the first sequence and a length of the second sequence, wherein anumber of candidates of the first sequence is configured to be largerthan a number of candidates of the second sequence, wherein a product ofthe number of candidates of the first sequence and the number ofcandidates of the second sequence is identical to a number of cellidentifiers supported by the wireless communication system, wherein asubcarrier spacing for the PSS and a subcarrier spacing for the SSS arebased on any one of a plurality of subcarrier spacings supported by thewireless communication system, and wherein a subcarrier spacing for aPhysical Broadcast channel (PBCH) that is related to the PSS and the SSSis configured to be equal to the subcarrier spacing for the PSS and thesubcarrier spacing of the SSS.